1. Field of the Invention
The present invention relates to radar systems. More specifically, the present invention relates to techniques for improving the performance of semi-active radar systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Semi-active radar systems include a transmitter on one platform and a receiver on another. Continuous and pulsed waveforms are currently used for semi-active radar transmission. The continuous wave (CW) technique involves the continuous transmission of a radar signal which is reflected off a target and received by the receiver on the second platform.
Pulsed transmission offers certain performance advantages over CW and involves the transmission of a sequence of radar pulses.
To secure the advantages of the pulse transmission, current semi-active designs operate asynchronously. Unfortunately, this mode of operation requires the receiver to be open to receive on a continuous basis. This impairs the noise performance of the system. To circumvent this problem, range gating of the receiver has been employed with limited success.
Range gating involves opening the receiver only when a return is expected from the target. This requires some indication of range to the target. Accurate range determination requires some facility for matching radar returns with the transmitted signal. Hence, range determination requires some knowledge of the timing of the transmitted signal. The current technique for acquiring critical timing data involves the processing the centerline frequency of the transmitted signal. While acquisition of timing data in a CW transmission scheme may be somewhat straightforward, it is problematic for pulse transmission schemes.
Thus, there is a need in the art for a semi-active radar receiver effective in the receipt of pulsed radar returns. More specifically, there is a need in the art for a semi-active radar receiver with means for providing some indication of the timing of the receipt of the transmitted pulse relative to the receipt of the return pulse and thereby provide a range determination.